ReferenceTypepublic abstract class ReferenceType extends Type | Super class for object and array types. |
| Constructors Summary |
|---|
protected ReferenceType(byte t, String s)
super(t, s);
| ReferenceType()Class is non-abstract but not instantiable from the outside
super(Constants.T_OBJECT, "<null object>");
|
| Methods Summary |
|---|
| public com.sun.org.apache.bcel.internal.generic.ReferenceType | firstCommonSuperclass(com.sun.org.apache.bcel.internal.generic.ReferenceType t)This commutative operation returns the first common superclass (narrowest ReferenceType
referencing a class, not an interface).
If one of the types is a superclass of the other, the former is returned.
If "this" is Type.NULL, then t is returned.
If t is Type.NULL, then "this" is returned.
If "this" equals t ['this.equals(t)'] "this" is returned.
If "this" or t is an ArrayType, then Type.OBJECT is returned.
If "this" or t is a ReferenceType referencing an interface, then Type.OBJECT is returned.
If not all of the two classes' superclasses cannot be found, "null" is returned.
See the JVM specification edition 2, "4.9.2 The Bytecode Verifier".
if (this.equals(Type.NULL)) return t;
if (t.equals(Type.NULL)) return this;
if (this.equals(t)) return this;
/*
* TODO: Above sounds a little arbitrary. On the other hand, there is
* no object referenced by Type.NULL so we can also say all the objects
* referenced by Type.NULL were derived from java.lang.Object.
* However, the Java Language's "instanceof" operator proves us wrong:
* "null" is not referring to an instance of java.lang.Object :)
*/
if ((this instanceof ArrayType) || (t instanceof ArrayType))
return Type.OBJECT;
// TODO: Is there a proof of OBJECT being the direct ancestor of every ArrayType?
if (((this instanceof ObjectType) && ((ObjectType) this).referencesInterface()) ||
((t instanceof ObjectType) && ((ObjectType) t).referencesInterface()))
return Type.OBJECT;
// TODO: The above line is correct comparing to the vmspec2. But one could
// make class file verification a bit stronger here by using the notion of
// superinterfaces or even castability or assignment compatibility.
// this and t are ObjectTypes, see above.
ObjectType thiz = (ObjectType) this;
ObjectType other = (ObjectType) t;
JavaClass[] thiz_sups = Repository.getSuperClasses(thiz.getClassName());
JavaClass[] other_sups = Repository.getSuperClasses(other.getClassName());
if ((thiz_sups == null) || (other_sups == null)) {
return null;
}
// Waaahh...
JavaClass[] this_sups = new JavaClass[thiz_sups.length + 1];
JavaClass[] t_sups = new JavaClass[other_sups.length + 1];
System.arraycopy(thiz_sups, 0, this_sups, 1, thiz_sups.length);
System.arraycopy(other_sups, 0, t_sups, 1, other_sups.length);
this_sups[0] = Repository.lookupClass(thiz.getClassName());
t_sups[0] = Repository.lookupClass(other.getClassName());
for (int i = 0; i < t_sups.length; i++) {
for (int j = 0; j < this_sups.length; j++) {
if (this_sups[j].equals(t_sups[i])) return new ObjectType(this_sups[j].getClassName());
}
}
// Huh? Did you ask for Type.OBJECT's superclass??
return null;
| | public com.sun.org.apache.bcel.internal.generic.ReferenceType | getFirstCommonSuperclass(com.sun.org.apache.bcel.internal.generic.ReferenceType t)This commutative operation returns the first common superclass (narrowest ReferenceType
referencing a class, not an interface).
If one of the types is a superclass of the other, the former is returned.
If "this" is Type.NULL, then t is returned.
If t is Type.NULL, then "this" is returned.
If "this" equals t ['this.equals(t)'] "this" is returned.
If "this" or t is an ArrayType, then Type.OBJECT is returned;
unless their dimensions match. Then an ArrayType of the same
number of dimensions is returned, with its basic type being the
first common super class of the basic types of "this" and t.
If "this" or t is a ReferenceType referencing an interface, then Type.OBJECT is returned.
If not all of the two classes' superclasses cannot be found, "null" is returned.
See the JVM specification edition 2, "4.9.2 The Bytecode Verifier".
if (this.equals(Type.NULL)) return t;
if (t.equals(Type.NULL)) return this;
if (this.equals(t)) return this;
/*
* TODO: Above sounds a little arbitrary. On the other hand, there is
* no object referenced by Type.NULL so we can also say all the objects
* referenced by Type.NULL were derived from java.lang.Object.
* However, the Java Language's "instanceof" operator proves us wrong:
* "null" is not referring to an instance of java.lang.Object :)
*/
/* This code is from a bug report by Konstantin Shagin <konst@cs.technion.ac.il> */
if ((this instanceof ArrayType) && (t instanceof ArrayType)) {
ArrayType arrType1 = (ArrayType) this;
ArrayType arrType2 = (ArrayType) t;
if (
(arrType1.getDimensions() == arrType2.getDimensions()) &&
arrType1.getBasicType() instanceof ObjectType &&
arrType2.getBasicType() instanceof ObjectType) {
return new ArrayType(
((ObjectType) arrType1.getBasicType()).getFirstCommonSuperclass((ObjectType) arrType2.getBasicType()),
arrType1.getDimensions()
);
}
}
if ((this instanceof ArrayType) || (t instanceof ArrayType))
return Type.OBJECT;
// TODO: Is there a proof of OBJECT being the direct ancestor of every ArrayType?
if (((this instanceof ObjectType) && ((ObjectType) this).referencesInterface()) ||
((t instanceof ObjectType) && ((ObjectType) t).referencesInterface()))
return Type.OBJECT;
// TODO: The above line is correct comparing to the vmspec2. But one could
// make class file verification a bit stronger here by using the notion of
// superinterfaces or even castability or assignment compatibility.
// this and t are ObjectTypes, see above.
ObjectType thiz = (ObjectType) this;
ObjectType other = (ObjectType) t;
JavaClass[] thiz_sups = Repository.getSuperClasses(thiz.getClassName());
JavaClass[] other_sups = Repository.getSuperClasses(other.getClassName());
if ((thiz_sups == null) || (other_sups == null)) {
return null;
}
// Waaahh...
JavaClass[] this_sups = new JavaClass[thiz_sups.length + 1];
JavaClass[] t_sups = new JavaClass[other_sups.length + 1];
System.arraycopy(thiz_sups, 0, this_sups, 1, thiz_sups.length);
System.arraycopy(other_sups, 0, t_sups, 1, other_sups.length);
this_sups[0] = Repository.lookupClass(thiz.getClassName());
t_sups[0] = Repository.lookupClass(other.getClassName());
for (int i = 0; i < t_sups.length; i++) {
for (int j = 0; j < this_sups.length; j++) {
if (this_sups[j].equals(t_sups[i])) return new ObjectType(this_sups[j].getClassName());
}
}
// Huh? Did you ask for Type.OBJECT's superclass??
return null;
| | public boolean | isAssignmentCompatibleWith(com.sun.org.apache.bcel.internal.generic.Type t)Return true iff this is assignment compatible with another type t
as defined in the JVM specification; see the AASTORE definition
there.
if (!(t instanceof ReferenceType))
return false;
ReferenceType T = (ReferenceType) t;
if (this.equals(Type.NULL))
return true; // This is not explicitely stated, but clear. Isn't it?
/* If this is a class type then
*/
if ((this instanceof ObjectType) && (((ObjectType) this).referencesClass())) {
/* If T is a class type, then this must be the same class as T,
or this must be a subclass of T;
*/
if ((T instanceof ObjectType) && (((ObjectType) T).referencesClass())) {
if (this.equals(T))
return true;
if (Repository.instanceOf(((ObjectType) this).getClassName(),
((ObjectType) T).getClassName()))
return true;
}
/* If T is an interface type, this must implement interface T.
*/
if ((T instanceof ObjectType) && (((ObjectType) T).referencesInterface())) {
if (Repository.implementationOf(((ObjectType) this).getClassName(),
((ObjectType) T).getClassName()))
return true;
}
}
/* If this is an interface type, then:
*/
if ((this instanceof ObjectType) && (((ObjectType) this).referencesInterface())) {
/* If T is a class type, then T must be Object (2.4.7).
*/
if ((T instanceof ObjectType) && (((ObjectType) T).referencesClass())) {
if (T.equals(Type.OBJECT)) return true;
}
/* If T is an interface type, then T must be the same interface
* as this or a superinterface of this (2.13.2).
*/
if ((T instanceof ObjectType) && (((ObjectType) T).referencesInterface())) {
if (this.equals(T)) return true;
if (Repository.implementationOf(((ObjectType) this).getClassName(),
((ObjectType) T).getClassName()))
return true;
}
}
/* If this is an array type, namely, the type SC[], that is, an
* array of components of type SC, then:
*/
if (this instanceof ArrayType) {
/* If T is a class type, then T must be Object (2.4.7).
*/
if ((T instanceof ObjectType) && (((ObjectType) T).referencesClass())) {
if (T.equals(Type.OBJECT)) return true;
}
/* If T is an array type TC[], that is, an array of components
* of type TC, then one of the following must be true:
*/
if (T instanceof ArrayType) {
/* TC and SC are the same primitive type (2.4.1).
*/
Type sc = ((ArrayType) this).getElementType();
Type tc = ((ArrayType) this).getElementType();
if (sc instanceof BasicType && tc instanceof BasicType && sc.equals(tc))
return true;
/* TC and SC are reference types (2.4.6), and type SC is
* assignable to TC by these runtime rules.
*/
if (tc instanceof ReferenceType && sc instanceof ReferenceType &&
((ReferenceType) sc).isAssignmentCompatibleWith((ReferenceType) tc))
return true;
}
/* If T is an interface type, T must be one of the interfaces implemented by arrays (2.15). */
// TODO: Check if this is still valid or find a way to dynamically find out which
// interfaces arrays implement. However, as of the JVM specification edition 2, there
// are at least two different pages where assignment compatibility is defined and
// on one of them "interfaces implemented by arrays" is exchanged with "'Cloneable' or
// 'java.io.Serializable'"
if ((T instanceof ObjectType) && (((ObjectType) T).referencesInterface())) {
for (int ii = 0; ii < Constants.INTERFACES_IMPLEMENTED_BY_ARRAYS.length; ii++) {
if (T.equals(new ObjectType(Constants.INTERFACES_IMPLEMENTED_BY_ARRAYS[ii]))) return true;
}
}
}
return false; // default.
| | public boolean | isCastableTo(com.sun.org.apache.bcel.internal.generic.Type t)Return true iff this type is castable to another type t as defined in
the JVM specification. The case where this is Type.NULL is not
defined (see the CHECKCAST definition in the JVM specification).
However, because e.g. CHECKCAST doesn't throw a
ClassCastException when casting a null reference to any Object,
true is returned in this case.
if (this.equals(Type.NULL))
return true; // If this is ever changed in isAssignmentCompatible()
return isAssignmentCompatibleWith(t);
/* Yes, it's true: It's the same definition.
* See vmspec2 AASTORE / CHECKCAST definitions.
*/
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